With a backdrop of the spread of the Internet, enhancement in the speed of packet forwarding devices, such as a router and a switch constituting the Internet communication systems, is sought for. The router and the switch are provided with a plurality of input lines and output lines, and when a packet is inputted thereinto from the input line, they decide an output line from a destination address in its header and forward the packet into the output line. Further, the router and the switch identify a flow that is a series of packet flows to which the packet belongs, and execute filtering processing of deciding passing/discarding of the packet, decision processing of priority in a network (in the present application, this processing is called a flow processing), etc. for each flow.
For enhancement in the speed of a packet forwarding device, since it is necessary to increase the number of devices, such as ASIC (Application Specific Integrated Circuit), or to increase the frequency, power consumption increases along with enhancement in the speed of the router and the switch. For this reason, it is required to reduce the power consumption and thereby minimize the increase in electric power accompanying the speed enhancement.
A method for realizing reduction in the power consumption of the packet forwarding device is described, for example, in JP-A-Hei11 (1999)-88458. The document describes that the packet forwarding device thereof monitors the presence of link connections with a plurality of lines that the packet forwarding device is equipped with, and turns on a power supply of a port control circuit for performing the packet processing when the link connection is found to exist. By turning off the power supply of the port control circuit that is not required to perform the processing, reduction in the power consumption of the packet forwarding device is realized.
Another method for realizing the reduction in the power consumption of the packet forwarding device is described, for example, in JP-A-Hei11 (1999)-234344. The packet forwarding device of this document has an access state monitoring unit that monitors a plurality of interface ports for accommodating the lines and access states of the interface ports, and a power supply control unit that decides whether currents are made to pass the respective interface ports according to respective monitoring states of the access state monitoring unit. By turning off the power supply of the interface port to which no access is made, the reduction in the power consumption is realized.
In addition, as a technology of suppressing the power consumption without sacrificing performance of network relay devices, there is JP-A-2007-228491.